title: Influenza pneumonia among adolescents and adults: a concurrent comparison between influenza A (H1N1) pdm09 and A (H3N2) in the post-pandemic period.
abstract: BACKGROUND
  Comparisons of the characteristics between the influenza A (H1N1) pdm09 and common seasonal influenza are important for both clinical management and epidemiological studies. However, the differences between pandemic and seasonal influenza during the post-pandemic period are poorly understood.
  
  
  OBJECTIVE
  The aim of our research was to investigate clinical and immune response differences between patients with influenza A (H1N1) pdm09 pneumonia and seasonal influenza A (H3N2) pneumonia in the post-pandemic period.
  
  
  METHODS
  During the first flu season in post-pandemic period, patients from Beijing Network for Adult Community-Acquired Pneumonia present A (H1N1) pdm09 or A (H3N2) influenza were compared concurrently in the aspects of clinical characteristics and inflammatory profile in acute phase.
  
  
  RESULTS
  Patients with A (H1N1) pdm09 influenza pneumonia showed a close mean age to A (H3N2) pneumonia (51 ± 20 vs 53 ± 16, mean ± standard deviation, years) but tended to have more underlying diseases (32.8% vs 10%, P=0.036). Although clinical characteristics were similar, no statistical difference were found in pneumonia severity index (PSI) score or intensive care unit admission rate or mortality, patients in A (H1N1) pdm09 cohort present higher levels of aspartate aminotransferase, lactase dehydrogenase (P=0.006, 0.018, respectively) in blood and also longer duration of fever than A (H3N2) cohort. Levels of interleukin (IL)-10 and IL-12 (p70) were higher in A (H1N1) pdm09 cohort (P=0.031, 0.047, respectively).
  
  
  CONCLUSIONS
  During the first post-pandemic flu season, patients with the A (H1N1) pdm09 pneumonia showed similar clinical characteristics but slightly higher disease severity and stronger systemic inflammatory response than A (H3N2) pneumonia.
authors.affiliation: Department of Infectious Diseases and Clinical Microbiology, Beijing Chao-Yang Hospital, Beijing Institute of Respiratory Medicine, Capital Medical University, Beijing, China.
authors.forename: Shu Qiao
authors.initials: SQ
authors.lastname: Yang
authors.forename: Jiu Xin
authors.initials: JX
authors.lastname: Qu
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
authors.forename: Xiao Min
authors.initials: XM
authors.lastname: Yu
authors.forename: Ying Mei
authors.initials: YM
authors.lastname: Liu
authors.forename: Bin
authors.initials: B
authors.lastname: Cao
mesh_terms: D000293:Adolescent; D000328:Adult; D002681:China / Q000453:epidemiology; D016207:Cytokines / Q000097:blood; D005260:Female; D006801:Humans; D015994:Incidence; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics*; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics*; D007251:Influenza, Human / Q000453:epidemiology* / Q000276:immunology / Q000821:virology; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D011024:Pneumonia, Viral / Q000453:epidemiology* / Q000276:immunology / Q000821:virology; D012367:RNA, Viral / Q000032:analysis*; D060888:Real-Time Polymerase Chain Reaction; D055815:Young Adult
chemical_list: D016207:Cytokines; D012367:RNA, Viral
keywords: influenza A (H1N1) pdm09; pneumonia; post-pandemic; seasonal influenza A (H3N2)